The present invention relates to optical-fiber type power transmission devices. The invention is particularly useful in infrared optical fibers for transmitting power in the order of 1-100 watts, e.g., for laser surgery; and the invention is therefore described below with respect to this application.
Optical fibers of the low-power type used for communication purposes are provided with an external cladding for purposes of protecting the fiber and also for purposes of decreasing the numerical aperture of the fiber, i.e., the divergence angle of the energy exiting from the fiber. It is also known to apply a metal ferrule or sleeve to the outer end of the optical fiber to protect it, and also to enable attachment of an accessory. Such ferrules are usually attached to the clad of the fiber end by mechanical means, e.g., by swaging or pinching the ferrule onto the fiber end.
However, such metal ferrules cannot be applied to unclad optical fibers used for transmitting power.
Thus, the ferrule if applied to uncladded fiber will absorb energy energizing from it unless the ferrule is of a transparent material suitable for that wavelength. Additional difficulties arise when using silver halide infrared transmitting fibers because of their high chemical reactivity.
Further, most of the power transmitting fibers have an external jacket to the fiber for gas cooling. Such an assembly attached with a ferrule would have drawbacks especially when used as a laser scalpel because of the difficult elongation of the jacket and fiber which could result during the manipulation of the assembly.
In addition, when using uncladded fiber having a large numerical aperature (i.e., a large divergence angle of the energy leaving the fiber tip), the distance from the fiber tip to the protruding protective ferrule must be kept at a minimum so that the highly divergent beam does not impinge on the ferrule. Further, the protective feature of the ferrule on the tip is effectively lost, especially in laser surgery procedure, where there is much debris, etc.
An object of the present invention is to provide an optical-fiber type power transmission device having advantages in the above respects.